1. Field of the Invention
The present invention relates to a method and apparatus for hydrating and transporting natural gas in the form of a hydrate. More particularly, the method and apparatus utilize the pressure and temperature conditions surrounding a submerged vessel to facilitate, maintain and reconvert a natural gas to and from a hydrate.
2. Description of the Prior Art
The knowledge that a natural gas is usable as a fuel has been known, as well as used as such, for a long time. A problem associated with its use is transporting if from the source to another place, since it ordinarily occupies a larger volume per available Btu than other fuels that are solid or liquid. One manner of overcoming this problem is to increase it pressure in the transfer container. Alternatively, the natural gas industry has utilized the process of reducing the temperature until the gas becomes a liquid at a predetermined pressure. This method results in liquid natural gas, LNG. Another way that is being considered by the natural gas industry is to partially oxidize methane, the major constituent of natural gas, to methanol in order to produce an easily transportable liquid.
In the first method--utilizing increased pressure--heavy containment devices are necessary. They are expensive to construct and, in the case of marine transport, difficult to maintain the requisite pressure. Likewise, if this method is used in the form of a cross-country pipeline, large compressors are necessary. This arrangement results in a large consumption of the natural gas itself to provide the pressure differential that moves the gas through the pipeline.
In the second method--manufacturing LNG--there is a very high investment required for the processing plant as well as the tankship, because of the equipment necessary to liquefy methane at low temperatures. As a result, large refrigeration loads utilize much of the gas sought to be transported. For instance, to convert a natural gas to a liquid consumes 12% to 14% of the gas. Another 6% to 8% of the source gas boils off during the sea transportation, though it is possible to utilize a portion of this boiled-off gas as a boiler fuel.
The third process--converting natural gas to methanol--also requires capital investments similar to those of LNG manufacture. Noteworthy of the conversion to methanol is that the conversion destroys up to 47% of the calorific value of the source gas.